From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A90E9C47242 for ; Mon, 31 May 2021 18:26:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8A3A36128A for ; Mon, 31 May 2021 18:26:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232363AbhEaS2I (ORCPT ); Mon, 31 May 2021 14:28:08 -0400 Received: from smtp-fw-9102.amazon.com ([207.171.184.29]:15273 "EHLO smtp-fw-9102.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230323AbhEaS1r (ORCPT ); Mon, 31 May 2021 14:27:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1622485567; x=1654021567; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=/Axf06XEDEdIr7ffwoaiyqSgaoMA0MLjFmh8K44LfN0=; b=LLQkj/56fqFYhHT8XtWTcHXWUSRVpTfztw1KVLvCopPbaJ+0JBz5WQh0 FpMGoR+cE1WWSdmlK3K/H4tFNF+9/wWZZYoCvjvbbU0P9DcHFtMlnpKa4 fh6a//gIOFjg7AmvgV7gQx5NLQyeXRF9VQXe+jIvMXU7hRvJOQFkcb96r s=; X-IronPort-AV: E=Sophos;i="5.83,238,1616457600"; d="scan'208";a="137675708" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-1e-57e1d233.us-east-1.amazon.com) ([10.25.36.210]) by smtp-border-fw-9102.sea19.amazon.com with ESMTP; 31 May 2021 18:26:00 +0000 Received: from EX13MTAUWC002.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan2.iad.amazon.com [10.40.159.162]) by email-inbound-relay-1e-57e1d233.us-east-1.amazon.com (Postfix) with ESMTPS id 5021D14021C; Mon, 31 May 2021 18:25:59 +0000 (UTC) Received: from EX13D29UWC001.ant.amazon.com (10.43.162.143) by EX13MTAUWC002.ant.amazon.com (10.43.162.240) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Mon, 31 May 2021 18:25:58 +0000 Received: from EX13MTAUWC001.ant.amazon.com (10.43.162.135) by EX13D29UWC001.ant.amazon.com (10.43.162.143) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Mon, 31 May 2021 18:25:58 +0000 Received: from dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com (172.19.206.175) by mail-relay.amazon.com (10.43.162.232) with Microsoft SMTP Server id 15.0.1497.18 via Frontend Transport; Mon, 31 May 2021 18:25:58 +0000 Received: by dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com (Postfix, from userid 6262777) id 926A91499; Mon, 31 May 2021 18:25:57 +0000 (UTC) From: Frank van der Linden To: CC: , Subject: [PATCH v2 4.14 03/17] bpf: Ensure off_reg has no mixed signed bounds for all types Date: Mon, 31 May 2021 18:25:42 +0000 Message-ID: <20210531182556.25277-4-fllinden@amazon.com> X-Mailer: git-send-email 2.23.4 In-Reply-To: <20210531182556.25277-1-fllinden@amazon.com> References: <20210531182556.25277-1-fllinden@amazon.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org From: Daniel Borkmann commit 24c109bb1537c12c02aeed2d51a347b4d6a9b76e upstream. The mixed signed bounds check really belongs into retrieve_ptr_limit() instead of outside of it in adjust_ptr_min_max_vals(). The reason is that this check is not tied to PTR_TO_MAP_VALUE only, but to all pointer types that we handle in retrieve_ptr_limit() and given errors from the latter propagate back to adjust_ptr_min_max_vals() and lead to rejection of the program, it's a better place to reside to avoid anything slipping through for future types. The reason why we must reject such off_reg is that we otherwise would not be able to derive a mask, see details in 9d7eceede769 ("bpf: restrict unknown scalars of mixed signed bounds for unprivileged"). Signed-off-by: Daniel Borkmann Reviewed-by: John Fastabend Acked-by: Alexei Starovoitov [fllinden@amazon.com: backport to 4.14] Signed-off-by: Frank van der Linden --- kernel/bpf/verifier.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 434829d4438b..9cb2c035f06d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2025,12 +2025,18 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env) } static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg, - u32 *ptr_limit, u8 opcode, bool off_is_neg) + const struct bpf_reg_state *off_reg, + u32 *ptr_limit, u8 opcode) { + bool off_is_neg = off_reg->smin_value < 0; bool mask_to_left = (opcode == BPF_ADD && off_is_neg) || (opcode == BPF_SUB && !off_is_neg); u32 off, max; + if (!tnum_is_const(off_reg->var_off) && + (off_reg->smin_value < 0) != (off_reg->smax_value < 0)) + return -EACCES; + switch (ptr_reg->type) { case PTR_TO_STACK: /* Offset 0 is out-of-bounds, but acceptable start for the @@ -2121,7 +2127,7 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, alu_state |= ptr_is_dst_reg ? BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST; - err = retrieve_ptr_limit(ptr_reg, &alu_limit, opcode, off_is_neg); + err = retrieve_ptr_limit(ptr_reg, off_reg, &alu_limit, opcode); if (err < 0) return err; @@ -2164,8 +2170,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value; u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value, umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value; - u32 dst = insn->dst_reg, src = insn->src_reg; u8 opcode = BPF_OP(insn->code); + u32 dst = insn->dst_reg; int ret; dst_reg = ®s[dst]; @@ -2205,13 +2211,6 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, dst); return -EACCES; } - if (ptr_reg->type == PTR_TO_MAP_VALUE) { - if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) { - verbose("R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n", - off_reg == dst_reg ? dst : src); - return -EACCES; - } - } /* In case of 'scalar += pointer', dst_reg inherits pointer type and id. * The id may be overwritten later if we create a new variable offset. -- 2.23.4